Well I suppose it had to happen sometime.

Went to visit some friends for a couple of hours, got back in the car, and turned the key to find the dash lit up like a disco.

Initial assessment is that I've got the orange warning triangle, flashing mileage, airbag & seatbelt 'do not drive' lights, S/S inop message & fuel cutoff inop message.

Faced with a 100 mile journey home, I do what any right-thinking 500 owner would do - utter an expletive. I could tell you what the expletive was, but then I'd have to ban myself.

I then do the second thing any regular reader of this forum would do. I disconnect the battery and go back inside for a cup of tea.

Half an hour later, with the battery reconnected and all the warning lights & messages still present, there's nothing else for it but to drive home; even more carefully than usual since the airbags & seat belt pretensioners most likely won't protect me if the worst happens. I keep off the motorways, just in case the donk decides to quit completely (I don't want an expensive recovery), but fortunately the journey is uneventful.

3hrs home at 50mph gives plenty of time for thinking.

All those messages suggest there's an issue with the airbag system (the fuel cutoff on the 500 is implemented in software in the airbag ECU).

Now most faults can usually be traced back to the last thing you did, but as all I did was to park up for a couple of hours (everything was fine before I stopped), I couldn't see how that was going to help. Certainly I couldn't think of anything I'd done that could possibly affect the airbags.

Except that I did do one thing - I opened and closed the rear hatch. The hatch wiring is a known fault, so opening the hatch could have triggered a loom failure, but as far as I can remember, there's nothing connected to the airbag system in that part of the loom. Still, I'm thinking that a stray live feed could have found its way onto one of the CANBUS lines and either damaged or upset the airbag ECU.

The first thing I did once safely home was to check the hatch wiring. Externally all looked well, but I know this can be deceptive as others have had frayed/broken inner cables with little or no grommet damage. And sure enough, peeling back the grommet shows clear evidence of loom failure .

The short term fix is to use the Panda. I've disconnected the battery for safety and, once I can resist the urge to blaspheme Fiat within earshot of small children, I'll go out and examine the hatch wiring properly.

There's no point doing anything else until I've sorted the wiring, but hopefuly once that's done, I'll be able to put it on diagnostics, reset the airbag ECU and do a proxi alignment and all will be well.

Right now I can only hope the damage to the wiring hasn't taken out some expensive bit of proprietary Fiat electronics.

Trip B still gave me 70+mpg for the journey back, so at least some of the electronics remain working.

I'll keep you all posted.

That's not good news, fingers crossed that it's only the wiring and nothing up or downstream that's affected.

I was going to post a link to repairing boot hatch cables from the forum, then thought NO maybe not the best time to do that.

gazz_bee said:

...fingers crossed that it's only the wiring and nothing up or downstream that's affected.

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Yup, fingers crossed.

There's been more than a few cases reported here of 500's needing replacement electronics; everything from radios through convergence units to airbag ECU's. I'm wondering now if at least some of these failures are the direct result of stray power spikes from faulty hatchback wiring.

This is a design fault that's been well known almost from the start of 500 production; IMO it should have been properly fixed by appropriate redesign many years ago.

I'm wondering how someone less familiar with the 500 would have been affected by this; if out of warranty, I'd say they could already be down £100 or so as Fiat's first response to that set of warning lights would likely be to put the car on diagnostics, not to check the hatch wiring.

I've been checking my hatch wiring regularly ever since this issue was first widely known; it's now clear that a simple visual check isn't sufficient and it's necessary to pull back the grommet in order to verify that all is still well. It's an essential check when buying a used 500.

If the 500 were an aircraft, there'd have been an AD (airworthiness directive) issued for this at least six years ago.

Officina red said:

I was going to post a link to repairing boot hatch cables from the forum, then thought NO maybe not the best time to do that.

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It's not repairing the wiring that's bothering me ....

jrkitching said:

Yup, fingers crossed.

There's been more than a few cases reported here of 500's needing replacement electronics; everything from radios through convergence units to airbag ECU's. I'm wondering now if at least some of these failures are the direct result of stray power spikes from faulty hatchback wiring.

This is a design fault that's been well known almost from the start of 500 production; IMO it should have been properly fixed by appropriate redesign many years ago.

I'm wondering how someone less familiar with the 500 would have been affected by this; if out of warranty, I'd say they could already be down £100 or so as Fiat's first response to that set of warning lights would likely be to put the car on diagnostics, not to check the hatch wiring.

I've been checking my hatch wiring regularly ever since this issue was first widely known; it's now clear that a simple visual check isn't sufficient and it's necessary to pull back the grommet in order to verify that all is still well. It's an essential check when buying a used 500.

If the 500 were an aircraft, there'd have been an AD (airworthiness directive) issued for this at least six years ago.

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are you an ex aircraft engineer jrkitching?


sorry to hear about the mess on the fiat 500 but if anyone can fix it, you can!
i hope to get rid of my fiat 500 as soon as possible, hopefully within the next year and give the mess to my brother who will get his driving licence within the next few months, let him drive it to the ground = )

ahmett said:

are you an ex aircraft engineer jrkitching?

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No, but I do have a pilot's licence.

If you think Fiat main dealer parts & labour charges are expensive, try visiting a licenced aircraft maintenance facility.

Getting a typical light aircraft through its annual check (the equivalent of an MOT) costs in the order of £5000, and that's if they don't find anything wrong with it.

Ouch, this could be expensive.

I'd have thought if it was a "soft" failure (such as a CAN bus wire being pulled to ground causing a comms blackout) then a restart would have cleared it (perhaps with a general warning remaining on as codes are logged), and a battery disconnect really should have cleared it.

Is there even CAN bus running through that grommit? Is it not just lights, wiper and demister in there?

There certainly seems to be a lot of wires in that grommit if CAN bus goes through there- if it was CAN bus would it not be just three wires- CAN+/CAN- and a +12V power feed with a CAN node inside the bootlid controlling power distrivution.

We no longer have Tiger Moth straightforward engineering. My flying friends could never understand me having a Fiat, but my first Fiat had the same sort of technology. With all the delicate electronics these days on all cars a small electrical failure can completely disable a car and can't be fixed on the road side. The quality of the components used is all important for reliability and Fiat seem to be cutting corners, going by the cost of diagnosis and replacement parts it is probably the only way they are making money. Some parts seem to be difficult to get for a car just a few years old, forcing owners to make do with poor quality look-alikes. The earlier models were basic, reliable, cheap to run and straightforward to maintain, now ease of maintenance is not considered in the design process.

Someone I know recently had the wiring loom in the driver's door do the same thing as Maybelline's hatch.

zanes said:

Is there even CAN bus running through that grommit? Is it not just lights, wiper and demister in there?

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I think there might be. Remember there's also the electrical hatch release to consider. I'd expect to find a CANBUS control wire for that.

First pictures soon.

jrkitching said:

No, but I do have a pilot's licence.

If you think Fiat main dealer parts & labour charges are expensive, try visiting a licenced aircraft maintenance facility.

Getting a typical light aircraft through its annual check (the equivalent of an MOT) costs in the order of £5000, and that's if they don't find anything wrong with it.

Click to expand...

yes but aircraft engineers are actually properly trained to check and fix things so that bad things dont happen . crashing an aircraft due to mechanical failure is a huge deal!

a fiat breaking down on the side of the road? no one cares = ) , most certainly fiat doesn't! actually they are happy if you break down, more money for them haha!

David Bliss said:

Someone I know recently had the wiring loom in the driver's door do the same thing as Maybelline's hatch.

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I also thought about this possiblity whilst driving home - opening the driver's door was the other thing I did when visiting my friends.

First pictures at the end of this post.

We've seen similar images of the wiring before, but look carefully at the grommet. It's completely intact and free of splits or breaks - there's simply no way you can know what's going on inside from an external inspection (I put a piece of white card behind it to get a better photo).

No point going anywhere with diagnostics or speculation until the hardware's fixed. I've got a lot on just now & the Panda works just fine, so I may park both car and problem for awhile. The battery is staying disconnected.

Whatever, owners of 500's out of warranty should be aware that they could land themselves an unexpected problem (& large bill, depending on how you go about fixing it), just by opening the rear hatch.

I'll bet any money you like that if you took a car with these dashboard issues to any main dealer, the first thing they'd do is put the car onto diagnostics.

My current advice to any 500 owner with an electrial problem is to peel back the grommet (you only need peel back the end that's attached to the tailgate, since that's where the breaks happen) and inspect these cables before doing anything else. Actually I'd go further and advise all 500 owners to do this check regularly, even if the car is otherwise well. A small dab of silicone grease or a quick spray of rubber lubricant on the grommet will make it easier to remove & replace the end. DO NOT USE WD40 - it will likely attack both wiring & grommet & make a bad situation worse.

If yours looks like mine, I'd suggest you don't attempt to drive, or even start the car. Just unclip the battery quick-release terminal, & call a mobile auto sparky if you can't or don't want to fix it yourself.

zanes said:

Is there even CAN bus running through that grommit? Is it not just lights, wiper and demister in there?

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There's some very light gauge cables in there (including the broken one) which surely can only be used for carrying control signals.

jrkitching said:

I also thought about this possiblity whilst driving home - opening the driver's door was the other thing I did when visiting my friends.

First pictures.

We've seen similar images of the wiring before, but look carefully at the grommet. It's completely intact and free of splits or breaks - there's simply no way you can know what's going on inside from an external inspection (I put a piece of white card behind it to get a better photo).

No point going anywhere with diagnostics or speculation until the hardware's fixed. I've got a lot on just now & the Panda works just fine, so I may park both car and problem for awhile. The battery is staying disconnected.

Whatever, owners of 500's out of warranty should be aware that they could land themselves an unexpected problem (& large bill, depending on how you go about fixing it), just by opening the rear hatch.

I'll bet any money you like that if you took a car with these dashboard issues to any main dealer, the first thing they'd do is put the car onto diagnostics.

My current advice to any 500 owner with an electrial problem is to peel back the grommet (you only need peel back the end that's attached to the tailgate, since that's where the breaks happen) and inspect these cables before doing anything else. If yours looks like mine, I'd suggest you don't attempt to drive, or even start the car. Just unclip the battery quick-release terminal, & call a mobile auto sparky if you can't or don't want to fix it yourself.

Click to expand...

That looks messy! Now let's just hope the same thing doesn't happen on the Panda!

Ouch- I hope that discolouration on the strands in the thick black wire isn't evidence of arcing?

That said, I bet that green and yellow wire that's totally snapped is screwing things up- could be a CAN signal.

zanes said:

Is it not just lights, wiper and demister in there?

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All of which are controlled by the CANbus system and body computer

ahmett said:

That looks messy! Now let's just hope the same thing doesn't happen on the Panda!

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The geometry of the Panda wiring is different (at least it is on the Mk3); the cable doesn't get repeatedly bent through such a sharp angle.

This is an inherent design fault, pure and simple. The wiring needs to either be rerouted so it bends more progressively or the specification of the wire needs to be changed to a type that's designed to cope with this degree of flexing.

I'll be repairing this with a different type of wire entirely. When I fix something, I like it to stay that way.

jrkitching said:

The geometry of the Panda wiring is different (at least it is on the Mk3); the cable doesn't get repeatedly bent through such a sharp angle.

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i am worried because i use the boot 4 times a day on average = )

ahmett said:

i am worried because i use the boot 4 times a day on average = )

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At least you have the advantage of a generally warmer climate. The wiring insulation becomes more brittle in cold weather. This kind of damage is progressive, like a fatigue failure; opening the hatch on a cold frosty morning will likely cause ten times the progression that opening it on a warm sunny day will.

jrkitching said:

At least you have the advantage of a generally warmer climate. The wiring insulation becomes more brittle in cold weather. This kind of damage is progressive, like a fatigue failure; opening the hatch on a cold frosty morning will likely cause ten times the wear that opening it on a warm sunny day will.

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I also think the fact that my car is 90% of the time parked in a garage helps a lot. so basically fiat made the car for the streets of Rome, not an overnighter in winter in Dorset = )

Most Easterly Pandas said:

All of which are controlled by the CANbus system and body computer

Click to expand...

If that was the case, would it not be wired as per:

zanes said:

just three wires- CAN+/CAN- and a +12V power feed with a CAN node inside the bootlid controlling power distrivution.

Click to expand...

As per JR's photo, it appears there are many wires- I can see at least 8 so it appears to be a mix of CAN bus (presumably, as already speculated, for the boot lock mechanism) and "traditional" switched feeds for the high level brake and number plate lights (and presumably wiper motor and heating element too- hence the very thick wire).